Current presence capabilities are generally based on knowing an identity of a particular user —e.g., the user identified by a particular E-mail address, such as abc@company.com. The ability to contact a person or service is limited to knowing the specific service or user desired. There are a number of possible scenarios, however, in which a user or system merely desires to know the presence of any service or user that meets certain criteria. The criteria about the user other than the user identification are referred to as the “context” of the person or service. This problem is relevant to technologies such as E-mail, instant messaging (IM), and voice over IP (VoIP).
In existing communication systems, it is normally necessary to be able to identify the entity with which one wishes to communicate (e.g., based on a person's E-mail address or telephone number). In some examples, it is possible to identify the entity with which communication is to occur based on some pre-defined label —e.g., a pre-defined group mailing list maintained by an E-mail system. It would be desirable, however, to communicate with one or more persons simply by identifying criteria that the target(s) of the communication are to satisfy.
Relevant background is provided by U.S. Published Patent Application No. 2006/0047742 (O'Neill, et al.), which is hereby incorporated by reference.